diff --git a/src/proto/if_ruby.pro b/src/proto/if_ruby.pro
index 7dedb22..352f155 100644
--- a/src/proto/if_ruby.pro
+++ b/src/proto/if_ruby.pro
@@ -1,9 +1,9 @@
 /* if_ruby.c */
-int ruby_enabled __ARGS((int verbose));
-void ruby_end __ARGS((void));
-void ex_ruby __ARGS((exarg_T *eap));
-void ex_rubydo __ARGS((exarg_T *eap));
-void ex_rubyfile __ARGS((exarg_T *eap));
-void ruby_buffer_free __ARGS((buf_T *buf));
-void ruby_window_free __ARGS((win_T *win));
+extern int ruby_enabled __ARGS((int verbose));
+extern void ruby_end __ARGS((void));
+extern void ex_ruby __ARGS((exarg_T *eap));
+extern void ex_rubydo __ARGS((exarg_T *eap));
+extern void ex_rubyfile __ARGS((exarg_T *eap));
+extern void ruby_buffer_free __ARGS((buf_T *buf));
+extern void ruby_window_free __ARGS((win_T *win));
 /* vim: set ft=c : */